Chair with calf support

ABSTRACT

A chair, particularly a wheelchair ( 1 ), has a detachable active calf support ( 4 ), which has a plurality of inflatable cushion members (A, B, C, D) providing a calf support surface for a person in the chair. The cushion members are parallel transverse tubes forming an array extending away from the chair seat ( 3 ). The chair has a control for inflating and deflating the tubes in a predetermined sequence.

TECHNICAL FIELD OF THE INVENTION

This invention relates to chairs, especially wheelchairs, and toattachments for such chairs.

BACKGROUND TO AND SUMMARY OF THE INVENTION

In essence, the present invention provides an active calf support, for aperson sitting in a chair, i.e. a support which applies a pressurevarying with time to regions of the calf, for stimulation of venousreturn in the lower limb. The applicants believe that such an activecalf support has not previously been proposed.

Beds having a plurality of cushion members, e.g. transverse tubes, whichare sequentially inflatable, are today well known. They are used forpatients who are inactive or not sufficiently active to turn themselvesregularly in bed, and who therefore run the risk of bed sores. Thesequential inflation of the cushion members applies intermittentpressure to the skin, thereby reducing or preventing the formation ofbed sores. An example of such a bed is the present applicants'GB-A-1595417. The present applicants have also sold active seats forparticularly wheelchairs, which have a plurality of cushions members inthe form of tubes extending from the front to the back of the chair, thechair carrying an air pump and a controller for sequentially inflatingand deflating the tubes, as described in WO94/07396 and U.S. Pat. No.5,277,414.

The present inventors have now realised that the provision of an activecalf support will have beneficial effects for a person who is seated forlong periods in a chair, such as a wheelchair. Because of the relativeinactivity of such a person, and because they cannot easily exercisetheir legs, there is a tendency for poor circulation of the blood in thelower leg. The present invention provides means to ameliorate this, andparticularly to stimulate venous return in the lower leg or lower legs.

It is mentioned that inflatable pads which are strapped around the calfare believed to be known, as also are boots containing inflatable padswhich contact the lower leg. It seems that these are intended to be usedby an active person, who desires massage of the muscles of the lowerleg, and are intended to be used with the lower leg in a verticalposition.

NL 7901599 discloses a chair with a tilting calf massaging cushion whichis driven by a motor via an eccentric.

According to the present invention in one aspect, there is provided achair having a seat and a calf support extending forwardly away from theseat, the calf support comprising a plurality of inflatable cushionmembers providing a support surface for at least one calf of a personsitting in the chair, the chair being provided with control means forinflating and deflating the cushion members in a predetermined sequence.

The cushion members may be any suitable size and shape. Tubes extendingtransversely to the direction of a leg of a person sitting in the chair(herein called “the forward direction”) are preferred. The cushionmembers are preferably in an array extending in the forward direction,and preferably there are at least three, more preferably at least fourcushion members in the array in the forward direction. For practicalreasons, relating to the construction of transverse tubes and therequirement for inflation and deflation, an array of four tubes in theforward direction is most suitable.

The length of each cushion member in the forward direction, e.g. thewidth of a tube whose longitudinal direction is transverse to theforward direction, is preferably in the range 40 mm to 100 mm, morepreferably 60 mm to 100 mm.

When there are at least three cushion members in the array in theforward direction, the control means for sequentially inflating anddeflating the cushion members is preferably arranged to inflate anddeflate the cushion members in a sequence such that a pressure wavetravels upwardly along the lower leg of the person sitting in the chair,i.e. towards the trunk of the person. The effect of inflation anddeflation of the cushion members in itself stimulates venous return andimproves muscle tone, by encouraging the normal physiological processesin the lower leg, and the provision of a pressure wave moving upwardlyalong the leg, may, it is thought, further encourage venous flow.Suitable control systems for inflating and deflating the cushion membersin the desired sequence are known, for example, from the patentspecifications mentioned above and from GB-A-2183471 and GB-A-2238237.

The calf support may be mounted on the chair so as to be movable betweentwo positions, i.e. a stowage position in which it is at or close tovertical and essentially does not support the calf of a person seated inthe chair and a use position in which the surface of the cushion memberswhich contact the calf extends in the forward direction at an angle ofat least 45° to the vertical, preferably at least 60° to the vertical.

The calf support may have an attachment portion, e.g. a frame portionwhich is releasably attachable to the chair, particularly to the frameof a wheelchair, and a support member for the cushion members which ismovable, e.g. rotatable about an axis, relative to the frame portion, tobring the cushion members from the stowage position to the use position.The cushion members may be adjustable in the forward direction along thesupport member. The angle of the support surface to the vertical in theuse position may be adjustable.

It will be understood that the active calf support provided by thepresent invention uses the weight of the lower leg of the user, toprovide pressure at the interface between the lower leg and the cushionmembers when inflated. When deflated, the cushion members are preferablybe vented to atmosphere, so that they apply only a residual pressure tothe calf, permitting free circulation in the lower leg.

The cushion members preferably have a sufficient width, transverse tothe forward direction, to accommodate both legs of the person in thechair. The cushion members may be suitably contoured in both the forwarddirection and the transverse direction, to provide a comfortable supportfor the user.

The present invention in another aspect provides a calf supportattachment for a chair, e.g. a wheelchair, comprising a plurality ofinflatable cushion members, a support for the cushion members supportingthem so that they provide a support surface suitable for at least onecalf of a person, and attachment means for mounting the attachment to achair so that a person sitting on the chair can rest a calf of a legextending away from the chair seat on the inflatable cushion member.Particularly, when intended for a wheelchair, the attachment meanspreferably is constituted by a frame portion securable to the wheelchairframe. Preferably the attachment includes a means for adjustablysupporting the cushion support at a predetermined angle relative to thevertical. Preferably the cushion support additionally has a stowageposition in which the cushion members substantially do not support thelower leg of a user.

Preferred and optional features of the calf support attachment of theinvention are discussed above.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

An embodiment of the present invention will now be described by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 is a side view of a wheelchair embodying the invention;

FIG. 2 is a side view of the calf support attachment of the wheelchairof FIG. 1, shown in its use position;

FIG. 3 is a plan view of the calf support portion of the attachment ofFIG. 2; and

FIG. 4 is an explanatory diagram, corresponding to a transverse sectionof the support construction of FIG. 3.

FIG. 1 shows a wheelchair 1 which has a conventional frame structure 2and has a seat 3 whose sitting surface is provided by a plurality ofinflatable tubes aligned in the front to back direction of the chair.Under the seat is mounted a control system and a pressurised air supplysystem (not shown). Reference should be made to our co-pendingapplication WO94/07396 for a full description of this seat and thecontrol and inflation system. The system includes its own power supplyin the form of one or more batteries.

Mounted on front members of the frame structure 2 is a calf supportattachment 4, which has bolt members 5 on a frame portion 6 (see FIG. 2)by which the attachment 4 is detachably secured to the wheelchair. Theframe portion 6 has two upright members, of which one can be seen inFIGS. 1 and 2, and cross-members (not shown).

Pivotally mounted on the frame portion 6, at the axis 7 is a rectangularsecondary frame 8 of which one longitudinal side is seen in FIGS. 1 and2, and whose pivoting position relative to the frame portion 6 iscontrolled and adjusted by means of a pair of conventional ratchetsupport devices 19, one of which is seen in FIGS. 1 and 2. The ratchetdevices 19 permit the secondary frame 8 to be located at any positionbetween a stowage position shown in FIG. 1 and an almost horizontal useposition shown in FIG. 2.

The secondary frame 8 has at its end a footrest 10 on which the user,while sitting in the wheelchair 1, may rest his or her feet,particularly when the attachment 4 is in its stowage position shown inFIG. 1.

The frame 8 carries a support board 9 which carries in turn an array offour inflatable tubes A, B, C, D of plastics material which have theirlongitudinal directions transverse to the forward direction of the calfsupport, i.e. the direction away from the front of the seat of thewheelchair. These four tubes A, B, C, D are formed of flexibleair-impermeable plastics material by a moulding process so that theyhave an approximately rectangular cross sectional shape as seen in FIG.2, when inflated. Their length in the forward direction, i.e. theirwidth transverse to their own longitudinal direction is 80 mm, so thatthe total length in the forward direction of the support surface whichthey provide for the leg of a user is about 32 cm. The length of thetubes is 35 cm.

FIGS. 3 and 4 show how the tubes A, B, C, D are mounted on the supportboard 9. FIG. 3 also shows air feed pipes 11 connected to the tubes A,B, C, D. In practice there are four such air feed pipes 11, one for eachtube A, B, C, D. The bottom surfaces of the tubes A, B, C, D areadhesively secured to a foam layer 12 which in turn is adhesivelysecured to a canvas backing sheet 13. Four straps 14 are stitched to thebacking sheet 13, under the tubes A, B, C, D, at the region 15 shown fortube C in FIG. 3, and each strap 14 has at its ends the components of abuckle 16, so that the four straps 14 can be strapped around the supportboard 9 and tightened, to secure the tube assembly in place. However,the exact location of the tube assembly on the board 9 can be adjusted,by moving the straps along the board 9.

The four tubes A, B, C, D are connected by the air feed pipes 11 to theair distributor (not shown) of the wheelchair. As mentioned above, thisair distributor is of a type already known in this art, and has a rotorand a stator, which by covering and uncovering of air passages controlthe inflation and deflation of the four tubes A, B, C, D of the calfsupport 4 as well as the inflation and deflation of the tubes of theseat 3 of the wheelchair. The wheelchair also carries a compressor forsupply of the inflation air, and a power supply for the air distributorand the compressor, and appropriate control equipment.

The inflation pressure supplied to the tubes A, B, C, D of the calfsupport 4 is the same as that supplied to the seat 3. Deflation is byventing to atmosphere, and this is controlled by the air distributordescribed above. Venting to atmosphere is sufficient to reduce theinterface pressure at the skin of the user to the desired low level. Theoverall inflation cycle for the four tubes A, B, C, D is 12 minutes, butthe length of this inflation cycle is not critical. The inflation cycleis chosen so as to provide a pressure wave moving slowly upwardly alongthe leg of the user, i.e. towards the seat of the wheelchair. A suitableinflation cycle is as follows

A deflated, B C D inflated 3 minutes

B deflated, A C D inflated 3 minutes

C deflated, A B D inflated 3 minutes

A B C inflated, D deflated 3 minutes

Between each of these four stages of the cycle, there may be a shortperiod (e.g. only a few seconds) when all four tubes A, B, C, D areinflated, or alternatively there may be a cross-over period when two ofthe tubes are partially inflated.

The interface pressure at the skin of the calf of the user is determinedby the pressure in the tubes A, B, C, D, since the contact area will bedetermined by the weight applied by the user to the tubes. The cyclicapplication of pressure and its withdrawal on deflation of the tube hasbeneficial physiological effects on the user, particularly stimulatingvenous return and improving muscle tone. The wave effect, i.e. theeffect of the pressure wave moving towards the wheelchair seat, is alsothought to assist venous return.

There may be a cloth covering over the top surface of the tubes A, B, C,D. The user may rest one or both legs on the support, and can freelymove the leg or legs across the support.

What is claimed is:
 1. A chair comprising: a seat; a calf supportreleasably and detachably mounted on the seat and extending in a forwarddirection from said seat, said calf support having at least fourinflatable cushion members arranged one closely adjacent the next in anarray, said cushion members of said array extending one after the otherin the forward direction from said seat and the array being of a lengthin said forward direction to provide a support surface for at least onecalf of a person sitting on said seat; and a control means for inflatingand deflating said cushion members automatically and cyclically in apredetermined sequence in which each one of said cushion members isperiodically deflated to thereby provide pressure relief to the calf ofthe person sitting on said seat while the other cushion members are inan inflated state the order of deflation of said cushion members in saidpredetermined sequence being such that a pressure wave travels in anupward direction along that the lower leg of the person sitting on saidchair.
 2. A chair according to claim 1 wherein said cushion members areparallel tubes extending transversely to the forward direction.
 3. Achair according to claim 1 wherein the calf support is mounted on thechair so as to be movable between a stowage position and a use position,the surface of the cushion members providing support for the userextending in the forward direction at an angle of at least 45° to thevertical in the use position.
 4. A chair according to claim 1 which is awheelchair (1).
 5. A chair as claimed in claim 1, wherein said cushionmembers have upper surfaces which are uncovered, such that said uppersurfaces make direct contact with the calf of the person.
 6. A chair asclaimed in claim 1, wherein said calf support is carried by said seatand is adjustable so as to vary its angular position relative to saidseat.